Fig. 3

The non-linear dose–response relationship between bilirubin and hypertension. Restricted cubic spine with 4 knots was performed to determine the bilirubin (STB, UCB, and CB)-hypertension dose–response relationship. The solid blue line represents the dose–response curve with multivariable Cox model, and the pink shading indicates the 95% confidence interval. STB, UCB, and CB exhibited bidirectional effects to hypertensive risk with the threshold concentration of 12.17 μmol/L, 8.59 μmol/L, and 3.47 μmol/L, respectively